This invention relates to a disc recording medium including an optical disc, magnetic disc, opticomagnetic disc, electrostatic disc, mechanical type disc or the like disc type recording medium for digital signal recording and, more particularly, to a disc recording medium capable of preventing occurrence of a burst error due to a scratch and dust on a disc in which data is repeatedly recorded for correction or compensation of an error when the disc is reproduced.
In recording formats used for a disc recording medium, there is a recording format according to which the same data is continuously recorded twice to ensure that one data can be read even when the other data cannot be read during reproduction of data from a disc and thereby enable correction or compensation of an error. For example, as shown in FIG. 2a, the first recording of the data starts at 110 and ends at 112. The second recording of the data starts at 112 and ends at 114.
In recording the same data twice on a CLV (constant linear velocity) type disc, there will arise a case where, as shown in FIG. 2A, first occurring data 4 and second occurring data which are of the same data are located in parallel to each other in their circumferential direction of a disc 12. In other words, the same data are located at tracks adjacent to each other. For example, the first frame recorded for the first time 116 and the first frame recorded for the second time 118 are in parallel with each other. If there occurs a scratch (or deposition of a foreign matter such as a black spot) 2 over the tracks on which the same data 4, 5 are respectively recorded on the disc 12, failure in reading of data will occur notwithstanding that the same data is written twice whereby a burst error occurs in a reproduced signal.
For preventing occurrence of such burst error, it is necessary to hold the length on the recording tracks for one of these occurring data below one circumference of the disc. For this purpose, a conventional data format is so made that, as shown in FIG. 2B, one data is divided to plural frames and respective divided frames are recorded twice. This conventional format, however, requires twice as long as undivided data for reading of one series of data frames with the result that the speed of reading of data becomes low. For example, the first frame of data recorded for the first time 120 is recorded after the start of the data 110. Immediately following the first frame of data recorded for the first time 120 is the first frame of data recorded for the second time 122. Following this is the next frame of data recorded for the first time 124 followed by the next frame of data recorded for the second time 126. This process continues until the last frame is recorded for the first time 128 followed by the last frame being recorded for the second time 130 at the end of the data 114.
It is, therefore, an object of the invention to provide a disc recording medium capable of preventing occurrence of a burst error due to a scratch on the digital recording disc in which data is repeatedly recorded for correction of or compensation for an error and also capable of reading data at a high speed.